Find a good beat-making program and install it on your computer. A program like this will allow you to place percussive notes in a visual grid and play them back in real time. In addition, you can loop the beats you create and add sonic effects to spice up the rhythm. Familiarize yourself with the program and all of its options.
Listen to recordings of rhythmically driven material to get an idea of what makes a good beat. A drumbeat should propel the song and keep time without getting in the way of the other musical instruments. For examples of excellent beats, listen to the music of artists such as Aphex Twin, Wu-Tang Clan and Sunny Day Real Estate.
Consider the type of music that you're making a beat for. If you're applying a drumbeat to a slow, plodding hip hop number, it will be drastically different from a beat used in a blistering punk rock song, both in tempo and style. The drumbeat should generally serve to enhance the song, and is rarely the primary focus. Exceptions to this occur, such as in some types of electronic music.
Write your beat in a time signature that fits with the song. The most common time signature used in music is 4/4, indicating that there are four beats per measure. For the absolute most basic drumbeat, you'll place a kick drum on the first and third beats with a snare drum on the second and fourth beats. Other popular time signatures include 6/8, with a kick drum on the first beat and a snare on the fourth.
Dress up your drum beat with additional fills and grooves. By starting with a basic drumbeat, you build a framework that you can expand upon. Try adding extra notes in between the basic notes you've already set up. For example, you could place an extra kick drum note after the existing ones. You can also try removing some of the notes from a more complex rhythm. Creating additional space within your drumbeat will give it a different feel.